It is often desirable to be able to power a portable electronic device without the need of a traditional electrical power cable that connects the device to an electrical power outlet. Electrical power cords tether devices and restrict their movement. Therefore, entangled power cords could cause confusion as to what cord is connected to a particular device and further delay usage in untangling the cords. These problems are particularly problematic when powering medical devices, such as electrically powered surgical tools that are used in an operating room environment.
Therefore, it is desirable to power portable electronic devices wirelessly without the need to plug the device into an electrical outlet. One such way of providing electrical power to a portable medical device is by using either primary or secondary electrochemical cells. However, when these cells become depleted through use of the device, the cells need to be replaced or recharged. In either case, use of the device is stopped to exchange or re-charge the cells. Such a delay in use of a medical device is not desirable, particularly when the device is being used to perform a surgical procedure.
In addition, to reduce, if not eliminate, the possibility of patient infection, surgical environments require that a sterile field be sustained continuously throughout a procedure. Generally, a “sterile field” is the space surrounding a surgical site at which a procedure is performed. Further, the sterile field extends to the front of the surgeon and any assisting personnel. This requirement extends not only to medical devices used in the sterile field, but also to power sources used by these medical devices. These medical devices may be used to perform a procedure, to monitor a patient, to monitor the surrounding environment, to provide visual, lighting, audio, recording and other such needs. Power sources are also used in personal protection systems that surgical personnel sometimes wear when performing a procedure. These personal protection systems may include a ventilation unit, a light source, or communication device. These devices generally utilize a rechargeable electrical power source that may be depleted and recharged multiple times.
Many electrical power sources used in the operating room include rechargeable cells. This allows the battery to be repetitively used. A unique set of problems arises when a sterilized surgical device or medical instrument also has a removable battery component that needs to periodically be removed from the device and recharged. Such battery components generally do not stay within the sterile field of a singular operation as they are intended to be used for multiple and different surgical procedures on different patients. As such, to reduce the risk of spreading disease and infection, the battery must either be sterilized before it can be reused in another surgical procedure or, if not sterilized, be transferred into a sterile environment within a sterile container. The former poses performance issues while the latter creates risk for breaching the sterile field. Therefore, there is a need to provide electrical power to recharge electrical power sources or directly power medical devices with minimal physical contact to thus reduce the possibility of contamination thereof.
Autoclave sterilization is a process in which pressurized heated steam is used to sterilize a surface. The autoclave process is often used to sterilize tools and instruments, particularly those used during a surgical procedure. In addition, the autoclave process is used to sterilize batteries and battery packs that are used during a surgical procedure. However, heat from the autoclave process may cause the cell chemistry to react or become modified thus resulting in an electrochemical cell or battery pack that does not perform optimally. For example, the autoclave process may cause a chemical reaction within the cell that results in a reduction of cell capacity.
Since it is important to keep the cell or battery pack sterilized, particularly, prior to use during a medical procedure, it is advantageous to minimize contact of the cell or pack to external surfaces after sterilization. As such, to ensure optimal sterilized conditions, cells and battery packs are typically charged prior to sterilization to minimize contact of the battery or battery pack with foreign surfaces, thus minimizing the possibility of breaching the sterile barrier. However, exposure of the cells to the heat of the autoclave process may result in electrical performance degradation as previously discussed. Therefore, it is ideal for a cell or battery pack to be charged after the autoclave sterilization process. Charging a cell or battery pack after the sterilization process would minimize the possibility that the cell's electrical performance may be degraded and, thus, would enable a longer usable life (cycle count).
Thus, there is a need to charge a battery or battery pack after an autoclave sterilization process without the need to physically contact the battery or pack to a foreign surface. One such means to recharge an electrical power source, such as an electrochemical cell or battery pack, is by using near field resonant inductive coupling to wirelessly transfer electrical energy to the electrical power source. Therefore, since electrical energy is transferred wirelessly, physical contact is reduced, and thus the possibility of contaminating the electrical power source is minimized.
In near field resonant inductive coupling, electrical energy is transferred wirelessly between two resonators that are tuned to resonate at about the same frequency. When the two resonators resonate, an oscillating magnetic field between the two is created that enables transfer of electrical energy therebetween. The electrical energy may thus be used to recharge an electrochemical cell or battery pack a distance away from the electrical power source. More specifically, near field resonant inductive coupling typically uses coupled electromagnetic resonators with long-lived oscillatory resonant modes to transfer electrical power. Near field resonant inductive coupling is further discussed in U.S. Pat. No. 8,461,719 to Kesler et al., which is incorporated herein in its entirety.